A senior U.S. envoy is in the North Korean capital to discuss Pyongyang's cooperation in efforts to peacefully end its nuclear weapons capabilities. The focus of the visit is to preview a promised declaration of all of the North's nuclear activities. VOA's Kurt Achin reports from Seoul.

U.S. Assistant Secretary of State Christopher Hill arrived in Pyongyang Monday for a rare visit to North Korea, where he is scheduled to spend the next three days consulting with senior officials about the North's nuclear weapons capabilities.

Hill is the senior U.S. delegate to six-nation talks aimed at ending those nuclear capabilities diplomatically. Earlier this year, Pyongyang promised the United States, Russia, Japan, South Korea and China it would declare all of its nuclear programs and materials as a step toward getting rid of them once and for all.

One of the main reasons for Hill's visit is to preview North Korea's nuclear declaration, which is expected to become formally available to all six nations. Before departing South Korea to fly to Pyongyang on a U.S. military jet, Hill told reporters he expects the North's document to be comprehensive.

"In the declaration, we have said all nuclear programs need to be declared and I think all means all," he said.

Hill says North Korea must address U.S. concerns about a possible secret uranium enrichment program which Pyongyang has never publicly admitted having. U.S. officials say senior North Korean authorities privately admitted to pursuing the program in 2002, in violation of a 1994 nuclear freeze agreement. North Korea restarted its plutonium-based weapons program within weeks after being confronted with U.S. evidence of the uranium program.

Hill says he has had extensive conversations with North Korean officials about the uranium issue, and expects to reach an understanding on it by the end of this year.

Hill is expected to visit the North's main plutonium-based nuclear facility at Yongbyon this week, to confirm the North's cooperation in disabling it in exchange for energy assistance.

However, experts say disabling Yongbyon is a relatively easy first step, compared with verifiably eliminating North Korea's existing stockpile of nuclear materials and weapons.

Hill says the United States has invested time and effort in building trust with North Korea - known formally as the DPRK. He says that trust must now be used to set up systems for verifying the North's nuclear disarmament.

"We need to be assured that we can verify what is done so as we go forward I believe there is an understanding by the DPRK that verification needs to be a part of any agreement," Hill said.

An announcement is expected any day now from Beijing, the host of the six-party talks, as to when the next round of meetings will take place. A new round could begin as soon as this week, after U.S. Assistant Secretary Hill travels to the Chinese capital from Pyongyang.